1. Field of the Invention
The present invention relates to a three-dimensional representation method and an apparatus capable of electronically reproducing a moving picture or video with a reduced amount of information on a three-dimensional image.
2. Description of the Prior Art
A liquid crystal shutter eyeglasses system shown in FIG. 1 is well known as a conventional system which is electrically rewritable, has a small amount of information and can display a three-dimensional video.
The working principle of the liquid crystal shutter eyeglasses system will be explained below.
In this liquid crystal shutter eyeglasses system, a three-dimensional object α1 is shot by cameras (α2, α3) from different directions to generate images (parallactic images) representing the three-dimensional object α1 as viewed from different directions.
The images taken by the cameras (α2, α3) are combined by a video signal converter α4 into a single video signal and fed into a two-dimensional display (for example, CRT display) α5.
An observer α7 views an image on the two-dimensional display α5 by wearing liquid crystal shutter eyeglasses α6.
Here, when the two-dimensional display α5 is displaying an image from the camera α3, the liquid crystal shutter eyeglasses α6 are made opaque on the left side and transparent on the right side. When the two-dimensional display α5 is displaying an image from the camera α2, the liquid crystal shutter eyeglasses α6 are made transparent on the left side and opaque on the right side.
By switching the above operations at high speed, the viewer feels he is watching parallactic images with both eyes because of the after image effect and therefore can see the object three-dimensionally because of binocular parallax.
Further, a volumetric system as shown in FIGS. 2A and 2B has been proposed as one of the conventional systems that are electrically rewritable, have a small amount of information and can display a three-dimensional video.
The working principle of this volumetric system is explained in the following.
In the volumetric type, as shown in FIG. 2B, a three-dimensional object β1 is sampled in the direction of depth as seen from the viewer to generate a set of two-dimensional images β2, which is reproduced in a depth direction on a time division basis on a volumetric three-dimensional display β3 to display a reproduced three-dimensional image β4.
The liquid crystal shutter eyeglasses system shown in FIG. 1, however, has a drawback that because of the required use of the liquid crystal shutter eyeglasses α6, the system, when used for teleconferencing, looks very unnatural.
Further, there are large inconsistencies among binocular parallax, convergence and focusing, which are physiological factors of stereoscopy.
That is, in the liquid crystal shutter eyeglasses system shown in FIG. 1, although the requirements of binocular parallax and convergence are almost met, this system will cause eyestrain because the focal plane is on the display surface.
In the volumetric type shown in FIGS. 2A and 2B, the depth positions of the reproduced three-dimensional object β1 are close to the surfaces on which images are actually displayed, and are also disposed between these surfaces, so that unlike the liquid crystal shutter eyeglasses system, this volumetric system can suppress contradictions among binocular parallax, convergence and focusing.
With the volumetric system, however, because the depth positions of the reproduced images are discrete, it is difficult to reproduce a three-dimensional object located at an intermediate position between the discreet display positions, or a three-dimensional object that varies greatly in the depth direction.